North Temperate Fish Research Articles

Can scale cortisol concentration be quantified non-lethally in wild fish species?

Cortisol, the primary glucocorticoid in fishes, is secreted into the bloodstream in response to stress. Circulating cortisol accumulates in scales, a durable calcified structure that can be easily sampled from many fish species. As such, the use of scale cortisol concentration (SCC) is currently being explored as a means of chronic stress biomonitoring in wild fishes. Scales serve an important role in fish physiology and thus the number of scales required for reliable cortisol analysis is a limiting factor in the non-lethal collection of such samples. To date, scale cortisol quantification has also only been performed non-lethally in captive fishes and due to differences in stress responsiveness SCCs likely differ in wild species. As such, this study aimed to (1) apply our fish scale processing and analysis protocol to wild fish species and (2) apply it to five north temperate fish species to provide information useful to future non-lethal scale sampling regimes. Cortisol was successfully measured in scales collected from wild northern pike (Esox lucius), walleye (Sander vitreus), whitefish (Coregonus clupeaformis), white sucker (Catostomus commersonii) and captive rainbow trout (Oncorhynchus mykiss). SCCs were significantly different between species and thus the sample mass required for reliable cortisol analysis differed as well. In addition to the size of the fish and the mass of their scales this is an important consideration for future scale cortisol analyses as these factors could make SCC an attainable non-lethal sample matrix in some species of fish but impractical in others.

Interactions of a temperate North American fish community with a very low head hydropower facility in Ontario, Canada

AbstractEfforts are underway to re‐evaluate the use of existing instream infrastructure (e.g., weirs, water control dams) for the purposes of hydroelectric generation, with new very low head turbine technology that is purportedly “fish friendly” making retrofitting a viable option. This is the case at Wasdell Falls on the Severn River, ON, Canada, where the first very low head (VLH) turbines in Canada were put into operation at a long‐standing low‐head dam site. There is little information regarding fish usage of areas upstream from these structures and how this may relate to entrainment risk. Therefore, we assessed the risk of entrainment based on fish use of the forebay areas upstream from the infrastructure, including the forebay of three operating VLH turbines. Acoustic telemetry was used to determine movements and entrainment events of eight north temperate fish species. Entrainment through the VLH turbines did not occur over the course of one year, however, several fish did move downstream via other paths (e.g., over the water control structure). Forebay use was exclusive to rock bass, smallmouth bass, northern pike and largemouth bass, whereas channel catfish, walleye, white sucker and pumpkinseed avoided the forebay. When near the dam, fish tended to select deeper areas located away from the VLH forebay. Fish use of the VLH forebay was limited to brief forays indicating exploratory movements rather than prolonged residence. The findings suggest that entrainment risk at this VLH turbine site is low for the species and life stages studied.

Effects of temperature and food availability on liver fatty acid composition and plasma cortisol concentration in age-0 lake sturgeon: Support for homeoviscous adaptation

Overwintering survival in north temperate fishes involves a series of adaptive responses to multiple environmental stressors. Homeoviscous adaptation includes changes in membrane lipid composition in response to reduced environmental temperature, which may be driven by changes in hormones involved in the endocrine stress response. We examined how reduced temperature and food availability may act in concert to influence hepatic fatty acid composition of phospholipids and triglycerides, in addition to plasma concentration of cortisol in age-0 lake sturgeon (A. fulvescens). At 153 days post hatch (dph), temperature was decreased from 16 °C to 1 °C at a rate of 0.5 °C per day, and at 200 dph, fish were either fed every other day or deprived of food for 45 days to simulate an overwintering event. Liver fatty acid composition of phospholipids and triglycerides were assessed before temperature manipulation (16 °C; 153 dph), when fish had been at 1 °C for 16 days (199 dph), 25 days of overwintering (225 dph) and 45 days of overwintering (245 dph). Plasma cortisol concentration was assessed at 153, 225 and 245 dph. When temperature was decreased, both mono- and polyunsaturated fatty acids significantly increased in phospholipids and triglycerides. Total omega-6 fatty acids significantly increased in phospholipids while total omega-3 fatty acids did not. During the simulated overwintering, there was no obvious difference in fatty acids of phospholipids and triglycerides between diet treatments and no difference in circulating cortisol concentration between baseline and post-stressed fish in the fasted group. Our results provide support for homeoviscous adaptation to cold temperatures in lake sturgeon.

Light climate and dissolved organic carbon concentration influence species-specific changes in fish zooplanktivory

Dissolved organic carbon (DOC) in lakes reduces light penetration and limits fish production in low nutrient lakes, reportedly via reduced primary and secondary production. Alternatively, DOC and light reductions could influence fish by altering their visual feeding. Previous studies report mixed effects of DOC on feeding rates of zooplanktivorous fish, but most investigators tested effects of a single concentration of DOC against clear-water, turbid, or algal treatments. We used a controlled laboratory study to quantify the effects of a DOC gradient (3–19 mg L−1) on average light climate and the zooplankton feeding rate of 3 common, north temperate fishes. Light availability, which was inversely related to DOC concentration, had a positive and linear effect on zooplankton consumption by juvenile largemouth bass (Micropterus salmoides) and bluegill (Lepomis macrochirus), explaining 22% and 28% of the variation in consumption, respectively. By contrast, zooplankton feeding rates by fathead minnow (Pimephales promelas) were best predicted by a nonlinear, negative influence of light (R2 = 0.13). In bluegill feeding trials we found a general trend for positive selection of larger zooplankton (Cladocera and Chaoboridae); however, the light climate did not influence the selection of prey type. Largemouth bass selected for larger-bodied zooplankton, with weak evidence that selectivity for large Cladocera changed from negative to neutral selection based on electivity values across the light gradient. Our results suggest that the effect of DOC on the light climate of lakes may directly influence fish zooplanktivory and that this influence may vary among fish species.

Antifreeze Activity in Temperate Fish from the East Sea, Korea

Antifreeze proteins and glycoproteins [AF(G)Ps] constitute a group of proteins that lower the freezing but not the melting points of aqueous solutions, enabling polar and north-temperate fish to survive in ice-laden environments. However, little is known about antifreeze activity in temperate fish; such work would extend our knowledge on the functions and evolution of AF(G)Ps. In the present study, we screened for antifreeze activity in temperate fish caught off the coast of Jumunjin (<TEX>$37.89^{\circ}N$</TEX>), Gangneung, Korea. Thermal hysteresis (TH) and the ability to inhibit ice recrystallization (IR) in blood, liver, and muscle samples from nine fish were examined to assess antifreeze activity. As the East Sea off the coast of Jumunjin is ice-free year round, we thought it most unlikely that the fish would express antifreeze proteins. Surprisingly, the blood of Pleurogrammus azonus and three types of tissue from Gymnocanthus herzensteini, Zoarces gilli and Kareius bicoloratus exhibited measurable TH values together with the ability to trigger characteristic morphological changes in ice crystals. Blood samples from the three species also evidenced ice recrystallization (IR) inhibition. This implies that AF(G)Ps or other antifreeze-like substances are present in temperate fish even under nonfreezing conditions. These results contribute to our understanding of the functions and origins of antifreeze activity in fish.

Evolution and origin of sympatric shallow-water morphotypes of Lake Trout, Salvelinus namaycush, in Canada's Great Bear Lake.

Range expansion in north-temperate fishes subsequent to the retreat of the Wisconsinan glaciers has resulted in the rapid colonization of previously unexploited, heterogeneous habitats and, in many situations, secondary contact among conspecific lineages that were once previously isolated. Such ecological opportunity coupled with reduced competition likely promoted morphological and genetic differentiation within and among post-glacial fish populations. Discrete morphological forms existing in sympatry, for example, have now been described in many species, yet few studies have directly assessed the association between morphological and genetic variation. Morphotypes of Lake Trout, Salvelinus namaycush, are found in several large-lake systems including Great Bear Lake (GBL), Northwest Territories, Canada, where several shallow-water forms are known. Here, we assess microsatellite and mitochondrial DNA variation among four morphotypes of Lake Trout from the five distinct arms of GBL, and also from locations outside of this system to evaluate several hypotheses concerning the evolution of morphological variation in this species. Our data indicate that morphotypes of Lake Trout from GBL are genetically differentiated from one another, yet the morphotypes are still genetically more similar to one another compared with populations from outside of this system. Furthermore, our data suggest that Lake Trout colonized GBL following dispersal from a single glacial refugium (the Mississippian) and support an intra-lake model of divergence. Overall, our study provides insights into the origins of morphological and genetic variation in post-glacial populations of fishes and provides benchmarks important for monitoring Lake Trout biodiversity in a region thought to be disproportionately susceptible to impacts from climate change.

Experimental evidence for trait utility of gill raker number in adaptive radiation of a north temperate fish

North temperate fish in post-glacial lakes are textbook examples for rapid parallel adaptive radiation into multiple trophic specialists within individual lakes. Speciation repeatedly proceeded along the benthic-limnetic habitat axis, and benthic-limnetic sister species diverge in the number of gill rakers. Yet, the utility of different numbers of gill rakers for consuming benthic vs. limnetic food has only very rarely been experimentally demonstrated. We bred and raised families of a benthic-limnetic species pair of whitefish under common garden conditions to test whether these species (i) show heritable differentiation in feeding efficiency on zooplankton, and (ii) whether variation in feeding efficiency is predicted by variation in gill raker numbers. We used zooplankton of three different size classes to investigate prey size dependency of divergence in feeding efficiency and to investigate the effect strength of variation in the number of gill rakers. Our results show strong interspecific differences in feeding efficiency. These differences are largest when fish were tested with the smallest zooplankton. Importantly, feeding efficiency is significantly positively correlated with the number of gill rakers when using small zooplankton, also when species identity is statistically controlled for. Our results support the hypothesis that a larger number of gill rakers are of adaptive significance for feeding on zooplankton and provide one of the first experimental demonstrations of trait utility of gill raker number when fish feed on zooplankton. These results are consistent with the suggested importance of divergent selection driven feeding adaptation during adaptive radiation of fish in post-glacial lakes.

Role of ambient light in structuring north-temperate fish communities: potential effects of increasing dissolved organic carbon concentration with a changing climate

The vertical light environment in freshwater lakes is sensitive to changes in dissolved organic carbon (DOC) concentrations, and DOC concentrations in most boreal lakes appear to be increasing as the climate changes. Understanding how DOC dynamics in lakes and watersheds are then linked to fish habitat is therefore critical to assessing the effects of climate change on fish communities. This paper reviews the evidence for climate-induced alterations to DOC in north-temperate watersheds and assesses the potential consequences of the resultant decreases in water clarity on fish production and community structure in small boreal lakes (&lt;500 ha). Although DOC increases are forecast for most boreal lakes, complex interactions between local climate, rates of terrestrial organic matter decomposition and runoff, existing water quality, species shifts in forest communities, and changing season lengths can all combine to affect the magnitude of water clarity declines that will occur in individual lakes. Elevated DOC concentrations will affect the availability of coldwater versus warmwater habitat and niche characteristics that are dependent on lake depth, water clarity, and the preferences and physiological tolerances of the individual species. The shifts in availability of suitable thermal habitat will in turn affect fish growth, production, and community composition. Range expansions for warmwater species and range reductions for coldwater species will likely occur in warmer, darker environments, with adverse consequences for some native species and likely advantages for invasive species such as smallmouth bass. Likewise, major shifts in trophic dynamics would accompany the darkening of boreal lakes as species-specific feeding efficiencies change and primary and secondary production are altered. From a beneficial perspective, elevated DOC concentrations will likely relieve some physiological stress in biota via protection against contaminant toxicity and ultraviolet radiation (UVR) exposure. As with many other disturbances, we need to view climate change impacts on fish communities as a multiple stressor problem and the potential impacts of the changing light environment needs to be given as much prominence as the study of stressors such as eutrophication and trace contaminants.

Phylogeography and the origins of range disjunctions in a north temperate fish, the pygmy whitefish (Prosopium coulterii), inferred from mitochondrial and nuclear DNA sequence analysis

Aim To investigate the degree of phylogeographical divergence within pygmy whitefish (Prosopium coulterii) and to test hypotheses concerning the origin of disjunct populations within North America.

Social familiarity and shoal formation in juvenile fishes

The potential influence of social familiarity in shoal-choice decisions was investigated in two sympatric species of north temperate fishes, juvenile banded killifish Fundulus diaphanus and juvenile bluegill sunfish Lepomis macrochirus. Groups of socially familiar and unfamiliar conspecifics were formed in the laboratory using wild-caught fishes. Juvenile F. diaphanus demonstrated a strong preference for familiar conspecific shoalmates, whereas juvenile L. macrochirus exhibited no preference for either unfamiliar or familiar conspecific shoalmates. The differential influence of familiarity on shoalmate choice in juveniles of these two species could be due to their different ecologies, local population densities and life histories.

Parasites and Diet of Trout-Perch (Percopsis omiscomaycus) from Northwest Territories, Canada, with Comments on the Range of Crepidostomum percopsisi Nelson, Choudhury and Dick 1997

The trout-perch, Percopsis omiscomaycus (Walbaum), is a widely distributed species in North America. Despite several compound community surveys, the northernmost survey of trout-perch parasites is from southern Manitoba, Canada. A total of 42 parasite species have been reported from trout-perch, with 2 species being strictly host specific. During limnological surveys of Sid and Blitzen lakes, Northwest Territories, Canada, 4 parasite taxa were recovered from trout-perch: Protozoan cysts, Diplostomum sp., Proteocephalus sp., and Crepidostomum percopsisi. The present study area is approximately 1,547 km northwest of Dauphin Lake, which is the northernmost documented range for C. percopsisi. These data provide further support for Halvorsen's “constant fauna” as a general rule for north temperate fish parasite communities. Comparisons with other trout-perch surveys from more southern portions of the biogeographic range suggest that parasite composition, at least in small, nutrient- and species-poor lakes at northern latitudes have decreased richness, despite trout-perch having a diverse diet compared with more southern surveys. The intermediate host of C. percopsisi is unknown. Other Crepidostomum spp. are transmitted through Ephemeroptera, which occur in the diet of the trout-perch from Blitzen and Sid lakes. However, the high prevalence of cladocerans in this study, similar to other published reports, might implicate cladocerans as a potential intermediate host for C. percopsisi.

“Big” concerns with high latitude marine protected areas (MPAs): trends in connectivity and MPA size

The success of marine protected areas (MPAs) as fisheries management tools in tropical latitudes has generated interest in their applicability and potential elsewhere. Here we suggest that dispersal and gene flow in marine fish populations (a primary biological consideration for marine reserve design) increases with latitude. For example, north temperate fish species at latitudes between 40° and 45° had about three times greater dispersal potential (planktonic larval duration (PLD), n = 96 species) and genetic homogeneity (FST, n = 100 species) than fish species near equatorial regions. Using the PLD and FST relationships, dispersal increases at a rate of ~8% per degree of latitude north or south of the equator. Therefore tropical MPAs should not serve as direct scalar templates in other regions, but rather should be used as a basis against which higher-latitude MPAs should be scaled. However, a review of 429 existing MPAs indicates that no such changes in reserve size have been implemented with respect to latitude. Fisheries managers must be prepared and willing to implement MPAs at large scales in high latitudes, either as single reserves or in a network, or else we lose the legitimacy of a new and promising management tool for conserving marine biodiversity in cold ocean regions.

SPECIES FLOCK IN THE NORTH AMERICAN GREAT LAKES: MOLECULAR ECOLOGY OF LAKE NIPIGON CISCOES (TELEOSTEI: COREGONIDAE: COREGONUS).

Studies on north temperate fish species indicate that new habitat availability following the last ice sheet retreat has promoted ecological speciation in postglacial lakes. Extensive ecophenotypic polymorphisms observed among the North American Great Lakes ciscoes suggest that this fish group has radiated through trophic adaptation and reproductive isolation. This study aims at relating the ecomorphological and genetic polymorphisms expressed by the Lake Nipigon ciscoes to evaluate the likelihood of an intralacustrine divergence driven by the exploitation of alternative resources. Morphological variation and trophic and spatial niches are characterized and contrasted among 203 individuals. Genetic variation at six microsatellite loci is also analyzed to appraise the extent of genetic differentiation among these morphotypes. Ecomorphological data confirm the existence of four distinct morphotypes displaying various levels of trophic and depth niche overlap and specialization. However, ecological and morphological variations were not coupled as expected, suggesting that trophic morphology is not always predictive of ecology. Although extensive genetic variability was observed, little genetic differentiation was found among morphotypes, with only one morph being slightly but significantly differentiated. Contrasting patterns of morphological, ecological, and genetic polymorphisms did not support the hypothesis of ecological speciation: the most ecologically different forms were morphologically most similar, while the only genetically differentiated morph was the least ecologically specialized. The low levels of genetic differentiation and the congruence between θ and φ estimates altogether suggest a recent (most likely postglacial) process of divergence and/or high gene flow among morphs A, C, and D, whereas higher φ estimates for comparison involving morph B suggest that this morph may be derived from another colonizing lineage exchanging little genes with the other morphs. Patterns of ecophenotypic and genetic diversity are also compatible with a more complex evolutionary history involving hybridization and introgression.

The Elimination of Radiocaesium from Fish

1. A general model for fish to predict the elimination rate of radiocaesium from a regression of water temperature, weight and a categorical variable for exposure (steady state, non-steady state), was developed from published data. 2. The generality of the new model for the elimination of radiocaesium from fish provides aquatic ecologists with the means to simplify greatly and improve existing methods for estimating ration for fish through the use of 137 Cs based bioenergetics models. 3. Comparisons of the general model with other less complete data suggests that the model is applicable to many of the common taxa of north temperate fish. 4. Fish whose tissue pools are equilibrated to ambient concentrations (steady state) appear to eliminate radiocaesium at a rate much slower than those in non-steady state. Application of previous laboratory models to steady state field situations would overestimate the elimination rate of radiocaesium by 1.4-fold.

Influence of Antifreeze Proteins on Behavior of Ice Crystals and Red Blood Cells during Solidification of Cell Suspensions with Cryoprotectant.

This study aims at clarifying fundamenentally the influence of antifreeze proteins (AFPs) on the cryopreservation of biological cells. AFPs are antifreeze agents present in Antarctic fishes and some north-temperate fishes, which protect them from freezing. The process of directional solidification of suspensions of human red blood cells was investigated microscopically, using physiological saline including 20%v/v glycerol with and without 20mg/ml AFPs. The red blood cells after freezing and thawing were also observed. Due to the addition of AFPs, the morphology of the ice crystal growing in the suspension changed dramatically from dendritic into spicular. The spiculate ice crystal caused mechanically strong interactions between the ice crystals and the red blood cells, and the resultant complete destruction of the red blood cells. This result suggests that the morphology of the ice crystal and its interaction with the cells are among the factors influencing cell survival through freezing.

The effects of disturbance and severe seasonal fluctuations in environmental conditions on north temperate shallow-water fish assemblages

The shallow-water fish populations at one disturbed and one undisturbed site in the Oslofjord, Norway were sampled with a beach seine from September 1981 to September 1982. The inner site (inner fjord; Hvervenbukta) is in the most polluted part of the fjord and has a heavy recreational usage during the summer months, the outer site (Ellingstad) is in a least polluted part of the fjord and has only sporadic recreational usage. Physical conditions at the two sites differ primarily in seasonal changes of dissolved oxygen levels (Hvervenbukta 3·3–11·1 ml O 2 1 −1 and Ellingstad 5·3–7·1 ml O 2 1 −1). Thirty-three fish species were caught at Ellingstad compared with only 23 at Hvervenbukta, with 0·61 similarity in species lists. Both sites had approximately equal numbers of resident and non-resident species. The mean density of individuals was much greater at Hvervenbukta (0·36 m −2) than at Ellingstad (0·04 m −2). Both sites showed a high dominance factor with a few species comprising the majority of the abundance. Overall species diversity ( H′), evenness ( F′) and species richness ( D) were greater at Ellingstad, consistent with the reduced disturbance. The overall range in seasonal similarity was relatively high for both sites as a function of the severe seasonal cycle in temperature (ice cover to approximately 20 °C). These relatively high variations are to be expected for north temperate fish assemblages. The range in the seasonal similarity index was greater at Hvervenbukta reflecting increased disturbance. There were dissimilar patterns in the seasonal cycles of community parameters at the two sites. Changes in population structure were largest during the period of recruitment of new year classes.